concept ETag header in category javascript

This is an excerpt from Manning's book JavaScript Application Design: A Build First Approach. Login to get full access to this book.

Once you’ve computed a hash, you can use it as a query string parameter in your page, /all.js?_=a38cbf9e, or you can append it to the filename, such as /a38cbf9e .all.js. Alternatively, you can add the hash to an ETag header. Choosing the right approach is a matter of identifying your needs. If you’re dealing with static assets such as JavaScript resources, then you’re probably better off hashing the filename (or its query string) and using an Expires header. If you’re dealing with dynamic content, setting the hash in an ETag is preferred.